The Alphabet Inc. unit is developing an all-in-one virtual-reality headset that doesn’t rely on a smartphone, computer or game console, according to people familiar with the matter. That would be a first in the rapidly evolving field.

Google also plans to release later this year a more advanced version of its $20 cardboard virtual-reality viewer that uses a smartphone as a screen, people familiar with the matter said. The new plastic viewer will include computer chips and sensors, these people said.

The new devices are the latest evidence of Google’s growing interest in virtual reality and will thrust the tech giant more fully into competition with Facebook Inc., whose Oculus unit plans to start shipping a $599 headset next month that runs off a personal computer.

HTC Corp. and Sony Corp. also plan headsets this year that require a PC or game console, while Samsung Electronics Co. began selling a $100 viewer in November that uses the company’s phones.

Google and others have shipped more than five million of Google’s cardboard viewers since late 2014, helping introduce many consumers to technology that immerses them in experiences that seem to be all around them. Industry insiders viewed the cardboard devices as an experiment, but recent moves suggest Google now thinks virtual reality could become a moneymaker in both hardware and software.

Companies across Silicon Valley and Hollywood have invested billions of dollars in the technology, hoping it has big potential in industries such as gaming, entertainment and education. Some tech executives view it as a “platform” for computing, much like a smartphone or a PC.

Yet virtual reality still appears years away from widespread adoption, in part because high-end headsets arriving this year require expensive PCs, while inexpensive smartphone viewers can give users headaches.

Google’s planned stand-alone headset appears to aim for a middle ground: a quality experience not tethered to an expensive PC or game console. Still, it is unclear whether many consumers are willing to pony up for another entertainment gadget.

One of the people familiar with the matter said the headset will include a screen, high-powered processors and outward-facing cameras. Google plans to use chips from startup Movidius Inc. that use the cameras’ feeds to track the motion of the user’s head, the person said. Other high-end headsets, like the Oculus Rift, tap the computing power of connected PCs and use external cameras to track users’ motion.

Movidius said in a written statement that it works with many companies on virtual reality and augmented reality, but declined to elaborate.

The timing of the stand-alone headset is unclear. One of the people familiar with the matter said it could be unveiled this year, while two others cautioned that it is early in development and Google could decide not to release it.

The company could unveil its new smartphone viewer at its annual developer conference in May, two people said.

To ensure that the device works with as many Android phones as possible, Google is retooling a new version of its Android mobile operating system to handle virtual-reality devices, those people said. One change would allow a phone to stay on even when it hasn’t been touched for a while, the people noted.

The Financial Times earlier reported news of Google’s new smartphone headset.